Ethylene propylene copolymer latices containing polar groups



United States Patent "ice 3,255 130 ETHYLENE PROPYLENECOPOLYMER LATICESCONTAINING POLAR GROUPS Gerald I. Keim, West Grove, Pa., and Stearns T.Putnam,

Wilmington, Del., assignors to Hercules Powder Company, Wilmington, DeL,a corporation of Delaware No Drawing. Continuation of application Ser.No. 113,616, May 31, 1961. This application Aug. 25, 1965, Ser. No.482,613

' 11 Claims. (Cl. 260-8) I This is a continuation of our copending U.S.application Serial No. 113,616, filed May 31, 1961, now abandoned.

The present invention relates to latices of modified ethylene-propylenecopolymers and, more particularly, to high solids latices ofethylene-propylene copolymers modified by the attachment thereto of aplurality of polar groups, and to the use of same as coating adhesivesin paper coating color compositions. I

The use of high solids ethylene-propylene latices as coating adhesives-for paper has been attended with difficulties for several reasons. Forexample, the adhesion of such copolymers to polar surfaces is only fair.Another reason is that in order to obtain stable latices such highconcentrations of dispersing agents must be used as to be incompatiblewith the copolymer and prevent the formation of coherent coatings.

It has now been discovered that by attaching a plurality of polar groupsto an ethylene-propylene copolymer, the resulting modified copolymer canbe used to form latices which are particularly useful as coatingadhesives in paper coating color compositions.

Accordingly, this invention relates to a latex of an ethylene-propylenecopolymer modified by the attachment thereto of a plurality of polargroups, to a paper coating color composition prepared from said latex,and to paper coated with said coating color.

The ethylene-propylene copolymers useful in the practice of thisinvention are the normally solid copolymers. These copolymers arematerials known to the art which can be prepared by copolymerizingethylene with propylene by any of several methods, such as the methodsdescribed in Belgian Patents 535,082; 538,782; 553,655; and 583,039; andUS. Patents 2,700,663 and 2,726,231; Those copolymers containing fromabout 21% to about 55% by weight propylene and having a reduced specificviscosity (RSV) of from about 0.8 to about 8.0 are most useful in thisinvention.

The term reduced specific viscosity, which is a function of molecularweight, is used herein to designate the sp/c determined on a 0.1%solution of the copolymer in decahydronaphthalene measured at 135 C.

It will be understood, of course, that the polymers of otheroz-O16fi1'1S having essentially equivalent properties can be used inplace of the ethylene-propylene copolymers. For example, thehomopolymers and copolymers of butene-l, pentene-l, etc., with ethylene,can be used to replace the ethylene-propylene copolymers in the modifiedlatices of this invention. These polymers can be prepared by the sarnegeneral methods used to prepare the copolymers of ethylene andpropylene.

Any polar compound, that is, any organic or inorganic compound whichwhen reacted with an ethylene-propylene copolymer affords polar groups,can be used in the practice of this invention. Exemplary of the polarcompounds that can be used are the organic unsaturated polar compoundssuch as maleic anhydride, methacrylic acid, acrylic acid, methylacrylate, acrylamide, acrylonitrile, allyl 'alcohol, allylamine, vinylpyridine, etc., and the inorganic polar compounds, as, for example,phosphorus halides be concentrated by known methods.

3,255,130 Patented June 7, 1966 such as phosphorus trichloride; alkalisulfites such as sodium sulfite; alkali bisulfites such as sodiumbisulfite; etc. These polar compounds can be reacted with anethylenepropylene copolymer by a free-radical mechanism using a compoundcapable of supplying free radicals at a given temperature and sufiicientheat to insure that free radicals will be formed. Exemplary of theattachment of polar groups are the following equations:

RH being an ethylene-propylene copolymer in each equation. The compoundused to supply free radicals and the temperature of the reaction willdepend on the polar compound being reacted and can readily be determinedby one skilled in the art. The number of polar groups required toimprove the properties of an ethylenepropylene copolymer so that it maybe used in coating color compositions varies over a wide range. However,in general, a sufiicient number of polar groups will be attached whenfrom about 0.05% to about 2.0% by Weight of polar compound is reactedwith an ethylenepropylene copolymer. Amounts substantially in excess of5% by weight do not improve adhesion sufliciently to Warrant theincreased cost.

The latices of this invention can be prepared by any one of a number ofprocedures. One convenient procedure is to prepare a solution of themodified ethylenepropylene copolymer and then form an oil-in-wateremulsion by mixing with water and a small amount of surfaceactive agent.The oil=in-water emulsion can then be stripped of the organic solvent orsolvents by steam distillation to give a dilute latex. This latex can,if desired, Latices having various total solids contents can beprepared; however, the total solids content will usually be from about40% to about 60% solids. I

In the preparation of a coated paper, it is conventional to prepare amixture of water and a pigment, such as clay or the like, optionallytogether with other materials such as,'for'exarnple, a solublepyrophosphate which may act as, a stabilizing agent. This mixture,otherwise known as a pigment slip or, since it generally contains clay,as a clay slip, is then compounded with a binder or coating adhesive,such as starch, to produce a composition known in the art as a coatingcolor which'is useful for coating paper. Considerable quantities of thecoating adhesive are used, and, accordingly, its composition andcharacteristics are of great importance in determining the quality ofthe finished paper. Important properties of the coating adhesive arethat it must impart to the finished paper a high degree of brightness,smoothness and gloss, and a good finish and feel after calendering. Inaddition to these basic qualities, there are various othercharacteristics that go far toward determining the value and utility ofcoating adhesives: (l) the coating color must flow smoothly and evenlyso that it may be applied to paper at sufficiently high speeds to beeconomical in ordinary coating processes and (2) the coating must havehigh strength to permit subsequent printing on the coated paper withoutpicking.

Now, in accordance with the present invention, there is utilized as acoating adhesive a composition, of matter comprising a latex of anethylene-propylene copolymer modified by the attachment thereto of aplurality of polar groups. This latex is mixed with a pigment slip and,optionally, other ingredients to form a coating color which when coatedon a paper surface provides brightness, smoothness and gloss, a goodfinish and feel after calendering, and high strength.

For optimum results in the coating of paper, it is preferred to preparea coating color having a total solids composition which is relativelyhigh, thus combining surface coating qualities with economicaloperations. Since the modified latices of the invention reduce theviscosity of coating colors, it is possible to use higher solids colorsand, hence,.to coat at a faster rate without increasing the dryingcapacity of the machine. total solids for the coating color is betweenabout 30% and about 70% solids with an optimum value of from about 50%to about 65%. If the modified latex is used as the sole adhesive in thecoating color, it will be present in an amount between about and aboutbased on the weight of clay, and preferably between about 6% and about18%. A composition containing an amount of total solids and adhesive inthis range is characterized by being readily applied to the surface ofpaper and by forming a highly resistant coating thereon. Thus, utilizingthe coating color according to this invention there is produced a coatedpaper which is highly satisfactory for use in printing operations and isresistant to disturbance of the coated surface through rubbing, pickingand the like. The latices of this invention can be used as the soleadhesive or merely to replace a part of the adhesive (starch or casein)in a conventional coating color. Where the modified latices are used toreplace a part of the starch or casein in a conventional coating colorthey will be present in an amount of at least 10% by weight based ontotal adhesives.

In place of the clay utilized as the pigment, there can be used otherpaper coating compositions and materials such as, for example, calciumcarbonate, titanium dioxide, or other coating pigments alone orpreferably with a clay base. The modification of the coating color usingthese materials will be within the knowledge of those skilled in theart.

The utility of the coating color is not limited to the type of paperpulp used, and, accordingly, it can be utilized with the various typesof kraft, soda, sulfite pulp, and the like, as well as with the variouschemical and semichemical paper pulps. By the same token, the inventioncan be utilized with various types of paper products such as paper,fiber board and the like. In all instances, the product produced ischaracterized by being relatively resistant to abrasion and having asurface of improved printing properties.

The general nature of the invention having been set forth hereinbefore,the following examples are presented for purposes of illustration, partsand percentages being by weight unless otherwise stated.

The Hercules P-n'nt Tester mentioned in the examples is an instrumentdeveloped for measuring the picking resistance of coated printingpapers. The instrument embodies the basic principles of a printingpress. Small strips of the test specimen are printed with an ink-likematerial under controlled conditions. The speed of printing is increasedby small increments until picking of a test strip occurs. For a morecomplete description of the print tester, see E. J. Barber et 3].,TAPPI, vol. 34, No. 10, October 1951, published by Technical Associationof the Pulp and Paper Industry.

Example 1 An ethylene-propylene copolymer having an RSV of 1.3 and apropylene content of 24.9 mole percent was prepared in chlorobenzeneusing a catalyst of diethylaluminum chloride and tert-butylorthovanadate. The

A preferred range of 4 resulting chlorobenzene solution had a solidscontent of 5.34%.

To 528 parts of the above chlorobenzene solution (which contained 28.2parts of ethylene-propylene copolymer) was added 1.35 parts of maleicanhydride and 1.67 parts of benzoyl peroxide. The reaction mixture wasagitated for 6 hours at a temperature of 50 C. and then cooled to 25 C.Then 200 parts of the resulting solution was emulsified by adding asolution of 1.5 parts of an alkyl sulfate anionic surface-active agentin 11.5 parts of 3.5% aqueous sodium hydroxide and vigorously agitating.After 5 minutes, 75 additional parts of water were added and thewater-in-oil emulsion inverted to form an oil-in-water emulsion having apH of 7.4. From this emulsion a dilute latex was formed by steamstripping the chlorobenzene. The resulting latex had a solids content of4.02% and an average particle size of 05 micron. It was concentrated bymixing with 28 parts of a 1% aqueous solution of carboxymethylcelluloseand allowed to stand overnight. Two layers formed. The bottorn layer,essentially water, was removed leaving a latex containing 58.6% solids.

A latex was prepared from the unmodified ethylenepropylene copolymer asdescribed above except that 1.25 times the amount of surface-activeagent was required to form the intermediate emulsion.

A clay slip was prepared by mixing 100 parts of fine kaolin coating claywith parts of Water and 0.3 part sodium pyrophosphate. After agitatingseveral minutes, a smooth suspension was obtained. To 73 parts of theclay slip was added 17.1 parts of the above-modified latex and a smallamount of anticoagulant to yield a smooth coating color containing 60%solids. A similar coating color was prepared from the latex containingunmodified copolymer in the exact same manner.

The thus prepared coating colors were coated on several sheets of ledgerstock using a standard paper coating machine and dried on a drum dryerto a moisture content of 6%. Coating weights of 5 lbs/ream were used.Each sheet was tested on the Hercules Print Tester using a viscosityrated printing ink. The coating color prepared with modifiedethylene-propylene copolymer failed at a printing speed of 4, while thecoating color prepared with unmodified ethylene-propylene copolymerfailed at a printing speed of 1. The coating containing modifiedethylene-propylene copolymer had very good wet-rub resistance asdetermined by rubbing a moistened surface across the coated paper andthen placing the surface against a piece of black paper. The amount ofcoating color which was rubbed off the paper onto the test surface andsubsequently transferred to the black paper was a qualitative indicationof the wet-rub resistance of the paper.

Example 2 An ethylene-propylene copolymer having an RSV of 2.3 and apropylene content of 21 mole percent was prepared in chlorobenzene usingthe catalyst described in Example 1. The resulting chlorobenzenesolution had a solids content of 5.32%.

To 500 parts of the above chlorobenzene solution was added 1.64 parts ofmaleic anhydride and 1.94 parts of benzoyl peroxide. The reaction wasagitated for 2 /2 hours at a temperature of 50 C., cooled to 25 C., andwashed 4 times with water to remove any unreacted maleic anhydride.

The solution of copolymer was then converted to a latex and tested as acoating color adhesive as described in Example 1.

A conventional coating color composition was prepared from astyrene-butadiene copolymer latex (containing 60 mole percent styrene)and tested under identical conditions. The coating color prepared withmodified ethylenepropylene copolymer performed as well as the standardcoating color prepared with styre'ne-butadiene copolymer in printingspeed tests.

Example 3 An ethylene propylene copolymer having an RSV of 2.0 and apropylene content of 26 mole percent was prepared in chlorobenzene usinga catalyst of tert-butyl orthovanadate and diethylaluminum chloride.When the solution had a solids content of 4%, the reaction was halted byadding 11% (by weight, based on copolymer content) of phosphorustrichloride.

The reaction vessel was evacuated, flushed with nitrogen, evacuatedagain, and then filled with oxygen. After agitating for 90 minutes asmall amount of diethanolamine was added and the reaction agitated anadditional minutes. The resulting product had a solids content of 4%. Ananalysis of the modified copolymer showed that it contained 0.46%phosphorus and 0.38% nitrogen. While its exact structure was not known,it was thought to contain phosphonamide groups.

The modified copolymer and the unmodified copolymer from which it wasprepared were each converted to a latex and then tested as coating coloradhesives. The coating color prepared from modified copolymer had betteradhesion for paper than the one prepared from unmodified copolymer.

Example 4 Four coating color-compositions, designated A, B, C, and D foridentification, were prepared from an ethylenepropylene copolymercontaining 29 mole percent propylene and having an RSV of 3.1 asfollows:

(A) To 800 parts of a 5% solution of the above copolymer inchlorobenzene was added 0.2 part of maleic anhydride at 50 C. After theanhydride dissolved, 0.4 part of benzoyl peroxide was added. Thereaction was agitated for 4 hours at 50 C. and then cooled and washedwith aqueous sodium carbonate and then water.

(B) The procedure of A was repeated except 0.4 part of maleic anhydrideand 0.8 part of benzoyl peroxide were used.

(C) To 800 parts of a 5% solution of the above copolymer inchlorobenzene was added 1.2 parts of allylamine at 50 C. After theallylamine dissolved, 5.1 parts of benzoyl peroxide was added. Thereaction was agitated {for 4 hours at 50 C. and then cooled and washedwith water to remove unreacted amine and benzoyl peroxide.

(D) A 5% solution of the above copolymer in chlorobenzene was preparedto be used'as a control.

Latices of A, B, C, and D described above were prepared as follows: To175 parts of each solution except D was added 4 parts of a 20% aqueoussolution of alkyl sulfate anionic surface-active agent (sodium laurylsulfate) with vigorous agitation. Solution D required 10 parts of thesurface-active agent for emulsification. After 1 minute agitation, 100additional parts of water was added and each water-in-oil emulsioninverted to form an oil-in-water emulsion. From these emulsions dilutelatices were formed by steam stripping the chlorobenzene solvent. Theresulting latices had a solids content of 5%. Each dilute latex wasconcentrated by mixing with 19.2 parts of a 1% aqueous solution ofcarboxymethylcellulose and allowed to stand until two layers formed. Ineach case the bottom layer was essentially water which was removedleaving latices having a solids content of about 50%.

Coating color compositons were prepared from the above latices asfollows: To each 6.7 parts of latex was added 0.5 part of 20% aqueoussodium caseinate solution, and then each latex was added to a blend of80 parts of 70% clay slip, 0.7 part sodium pyrophosphate, and 33.6 partsof a 20% aqueous starch solution. Each of the resulting coating colorswere then coated on ledger 6 stock and tested as described in Example 1.The results are tabulated below.

Failing speed,

Example 5 There coating color compositions, designated A, B, and C foridentification, were prepared from an ethylenepropylene copolymercontaining 43 mole percent propyle'ne and having an RSV of 3.0 asfollows:

(A) To 600 parts of a 5% solution of the above copolymer in ahydrocarbon solvent (97.1% saturated and having a boiling range of 9499C.) was added 1.5 parts of jallylamineand 6.36 parts of benzoyl peroxideat 50 C. The reaction was agitated for 4 hours at 50 C. and then cooledand washed with water.

(B) To 600'parts of a 6.25% solution of the above copolymer inchlorobenzene was added 1.87 parts of 2-vinyl pyridine and 4.32 parts ofbenzoyl peroxide at 50 C. The reaction was agitated for 4 hours at 50 C.and then cooled and washed with Water.

' (C) A 5% solution of the above copolymer in chlorobenzene was preparedto be used as a control.

Latices and then coating color compositions were prepared from the abovesolutions as described in Example 4. Each of the resulting coatingcolors was then coated on ledger stock and tested as described inExample 1. The results are tabulated below.

Failing speed,

preparation of tire cord coating compositions, emulsion paints,resilient concrete, binder for cork, wood, leather bufiings, etc.

What we claim and desire to protect by Letters Patent 1s:

1. A latex of an ethylene-propylene copolymer modified by the attachmentthereto of a plurality of polar groups, said polar groups having beenattached by reacting said copolymer with a polar compound selected fromthe group consisting of maleic anhydride, methacrylic acid, acrylicacid, methyl acrylate, acrylamide, acrylonitrile, allyl alcohol,allylamine, vinyl pyridine, phosphorus halides and alkali sulfites, saidcopolymer having an RSV of from about 0.8 to about 8.0 and said polargroups not being substantially in excess of 5% by weight of thecopolymer.

2. The composition of claim 1 wherein the polar groups are attached byreacting the ethylene-propylene copolymer with maleic anhydride.

3. The composition of claim 1 wherein the polar groups are attached byreacting the ethylene-propylene copolymer with allylamine.

4. The composition of claim 1 wherein the polar groups are attached byreacting the ethylene-propylene copolymer with 2-vinyl pyridine.

5. The composition of claim 1 wherein the polar groups are attached byreacting the ethylene-propylene copolymer with phosphorus trichloride.

6. A paper coating color comprising an aqueous dispersion of substantialquantities of a paper coating pigment and an adhesive, said adhesivecontaining at least 10% by weight of a latex of an ethylene-propylenecopolymer modified by the attachment thereto of a plurality of polargroups, said polar groups having been attached by reacting saidcopolymer with a polar compound selected from the group consisting ofmaleic anhydride, methacrylic acid, acrylic acid, methyl acrylate,acrylamide, acrylonitrile, allyl alcohol, allylamine, vinyl pyridine,phosphorus halides and alkali sulfites, said copolymer having an RSV offrom about 0.8 to about 8.0 and said polar groups not beingsubstantially in excess of 5% by weight of the copolymer.

7. The composition of claim 6 wherein said adhesive is a mixture ofstarch and at least 10% by Weight of said latex.

8. The composition of claim 6 wherein said adhesive is a mixture ofcasein and at least 10% by weight of said latex.

9. The composition of claim 6 wherein said adhesive is essentiallyentirely said latex.

10. In a process of coating a paper with a coating color comprising anaqueous dispersion of substantial quantities of a paper coating pigmentand an adhesive, the improvement of using an adhesive containing atleast 10% by weight of a latex of an ethylene-propylene copolymermodified by the attachment thereto of a plurality of polar groups, saidpolar groups having been attached by reacting said copolymer with apolar compound selected from the group consisting of maleic anhydride,

'methacrylic acid, acrylic acid, methyl acrylate, acrylamide,acrylonitrile, allyl alcohol, allylamine, vinyl pyridine, phosphorushalides and alkali sulfites, said copolymer having an RSV of from about0.8 to about 8.0 and said polar groups not being substantially in excessof 5% by weight of the copolymer.

11. A coated paper comprising a paper web having on the surface acoating comprising a paper coating pigment and an adhesive, saidadhesive containing at least 10% by weight of a latex of anethylene-propylene copolymer modified by the attachment thereto of aplurality of polar groups, said polar groups having been attached by reacting said copolymer with a polar compound selected from the groupconsisting of maleic anhydride, methacrylic acid, acrylic acid, methylacrylate, acrylamide, acrylonitrile, allyl alcohol, allylamine, vinylpyridine, phosphorus halides and alkali sulfites, said copolymer havingan RSV of from about 0.8 to about 8.0 and said polar groups not beingsubstantially in excess of 5% by weight of the copolymer.

No references cited.

WILLIAM H. SHORT, Primary Examiner.

1. A LATEX OF AN ETHYLENE-PROPYLENE COPOLYMER MODIFIED BY THE ATTACHMENTTHERETO OF A PLURALITY OF POLAR GROUPS, AND POLAR GROUPS HAVING BEENATTACHED BY REACTING SAID COPOLYMER WITH A POLAR COMPOUND SELECTED FROMTHE GROUP CONSISTING OF MALEIC ANHYDRIDE, METHACRYLIC ACID, ACRYLICACID, METHYL ACRYLATE, ACRYLAMIDE, ACRYLONITRILE, ALLYL ALCOHOL,ALLYLAMINE, VINYL PYRIDINE, PHOSPHORUS HALIDES AND ALKALI SULFITES, SAIDCOPOLYMER HAVING AN RSV OF FROM ABOUT 0.8 TO ABOUT 8.0 AND SAID POLARGROUPS NOT BEING SUBSTANTIALLY IN EXCESS OF 5% BY WEIGHT OF THECOPOLYMER.
 6. A PAPER COATING COLOR COMPRISING AN AQUEOUS DISPERSION OFSUBSTANTIAL QUANTITIES OF A PAPER COATING PIGMENT AND AN ADHESIVE, SAIDADHESIVE CONTAINING AT LEAST 10% BY WEIGHT OF A LATEX OF ANETHYLENE-PROPYLENE COPOLYMER MODIFIED BY THE ATTACHMENT THERETO OF APLURALITY OF POLAR GROUPS, SAID POLAR GROUPS HAVING BEEN ATTACHED BYREACTING SAID COPOLYMER WITH A POLAR COMPOUND SELECTED FROM THE GROUPCONSISTING OF MALEIC ANHYDRIDE, METHACRYLIC ACID, ACRYLIC ACID, METHYLACRYLATE, ACRYLAMIDE, PHOSPHORUS HALIDES AND ALKALI SULFITES, SAIDCOPOLYMER HAVING AN RSV OF FROM ABOUT 0.8 TO ABOUT 8.0 AND SAID POLARGROUPS NOT BEING SUBSTANTIALLY IN EXCESS OF 5% BY WEIGHT OF THECOPOLYMER.
 8. THE COMPOSITION OF CLAIM 6 WHEREIN SAID ADHESIVE IS AMIXTURE OF CASEIN AND AT LEAST 10% BY WEIGHT OF SAID LATEX.